In the semiconductor industry, the main challenge in dealing with the surfaces of copper (Cu) substrates is such surfaces when exposed to the environment, even to a clean room environment, form a thin surface oxide layer, for example a thin surface layer containing Cu(OH)2, CuO, Cu2O, and CuCO3. Proper cleaning of the copper surface is needed to properly deposit other layers in a device stack. Typical methods of cleaning the oxidized Cu surfaces include a wet chemical clean, plasma cleaning, or an ozone treatment. However, the inventors have observed that wet cleaning processes can undesirably contaminate the copper surface due to the usage of various acids and other chemicals. A plasma based cleaning process undesirably can damage the copper surface, especially when a thin layer of copper, for example about 25 nm to about 50 nm, is treated.
Accordingly, the inventors have developed improved methods and apparatus for in-situ cleaning of copper surfaces and deposition and removal of self-assembled monolayers.